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Linear motion devices are known in which a car, carriage or other device is moveable along a linear path. The motion may be along a vertical path as in a hoist or elevator, or along a horizontal path as in movement of cars along a rail such as in automatic transport equipment in a manufacturing facility. Also in copying and printing machines. Similar movement also occurs in copying and printing machines in which a print head or other mechanism is moveable along an intended path. Electrical signals transferred to or from a moving carriage from a stationary source employ interconnecting cables which are usually disposed within a defined area to not interfere with movement of the carriage and to prevent damage to the cable during carriage motion. The cables or electrical wires are often disposed in association with a multi-link chain which is moveable along the travel path of the carriage and which guide the electrical cabling. However, such chains can collect dirt and the links rubbing together can generate dirt and debris which affects the overall cleanliness of the environment in which the cable is employed. A clean environment is especially useful and often necessary for many manufacturing and other fabrication processes in which a moving carriage is utilized. A particular example is in semiconductor manufacturing in which cleanliness is imperative for fabricating satisfactory semiconductor wafers. Such multi-link chains are also unable to be self supporting over long lengths of travel and thus require supporting trays, platforms, or rollers along a travel path where without such support the chain and accompanying cable would sag or not remain in intended position.
In accordance with the present invention, a self supporting electrical cable is provided which is especially of use with linear motion devices. The cable is in the form of a band having a crowned or curved cross-section. The band is self supporting and is typically employed in a looped configuration. The band is composed of a Mylar or other plastic or electrically insulating laminate with electrical conductors and reinforcing elements disposed therein. The conductors are typically copper and the reinforcing elements are typically stainless steel. In use the cable is usually folded back on itself 180xc2x0 to provide a loop configuration with a fixed radius loop end in which the loop is moveable along the direction of travel. One end of the cable is connected to the linear motion device or other moving device, and the other end of the cable is connected to a fixed device or apparatus, which can include a source of electrical energy. The conductors of the flat cable can be shielded if desired to minimize electrical interference. The camber or crown of the cable stiffens the cable such that the cable is self supporting even when disposed horizontally along its length or at an inclined position. The cable or band does not have any elements which rub against each other as do the links of a conventional cable chain and thus the present invention provides a cleaner and also quieter cable structure.
Another embodiment of the invention employs a center area of the band which is of a magnetically permeable material. This center area can engage a magnetic strip or series of magnets located along a travel surface to retain the band in position, which is useful especially over relatively long travel distances.